Method and apparatus for applying a threaded cap to a threaded neck of a container

ABSTRACT

There is described a method of applying a threaded cap to a threaded neck of a container. The method comprises the steps of placing the cap on the neck of the container, rotating the cap relative to the neck in an opening direction whilst supporting the cap with respect to the neck; and applying the cap to the neck so as to achieve substantial thread engagement.  
     There is also described an applicator for applying a threaded cap to a threaded neck of a container and reverse drive mechanism for use with an applicator.

[0001] The present invention relates to a method and apparatus forapplying a threaded cap to a threaded neck of a container.

[0002] The use of a threaded cap to close a container, where thecontainer has a correspondingly threaded neck is well known. Duringpackaging, after the container has been filled, it is necessary to applythe cap to the neck of the container to seal the contents of thecontainer and prevent leakage. Typically this is a two stage process.

[0003] Initially the cap is placed on the neck of the container withoutsubstantial engagement of the threads. There are two commonly usedmethods of placing the cap on the container neck. In the first method,known as the “pick and place” method, a cap is collected by a cappinghead. The capping head suspends the cap in a substantially horizontalplane and the cap is either lowered onto the neck of the container orelse the container is raised up to meet the cap.

[0004] The second method is known as the “pick-off” method. In thismethod, rather than the cap being suspended in a capping head and placedon the container neck, the caps are suspended above where the containersare transported, such that each cap is inclined with respect to thedirection of motion of a respective container. The incline of the cap issuch that the container neck contacts the inside of the cap and removesthe cap from the suspension point. The cap is thereby placed on the neckwithout substantial engagement of the threads. Once the suspended caphas been removed from the suspension point another cap takes its placeand the process is repeated with the next container.

[0005] Once the cap has been placed on the neck of the container thereare then two common ways of applying the cap onto the neck of thecontainer such that the threads are in substantial engagement. The firstmethod of application is by means of an axially downward force whichcauses the threads of the cap to slide over those of the container andthen interengage.

[0006] A second method of applying the cap to the container neck is byrotating the cap relative to the neck of the container. This rotationtakes place in the direction of rotation of the threads and is designedso that a predetermined torque is achieved between the cap and thecontainer with the result that the threads are in substantialengagement.

[0007] A common problem with the use of the previously described methodsis that if the cap is not placed on the neck so that the threads of thecap are in alignment with those of the neck, the subsequent applicationof the cap can result in cross-threading.

[0008] In addition, since the neck and cap are commonly made ofdifferent materials, with different hardnesses, if the threads areinitially cross-threaded, the subsequent forced application of the capto the neck by either method can result in the threads becoming damaged.This in turn may lead to subsequent problems with leakage encountered byretailers, distributors and consumers alike. Also, if the threads aredamaged, there may be a problem with leakage even if the cap is removedand subsequently applied correctly.

[0009] It is also known that when the threads of the cap and neck arecross-threaded the removal of the cap may be significantly moredifficult than if the threads are in alignment. This can cause problemsfor users with weakened capability such as the elderly or sick.

[0010] It is therefore desired to provide an apparatus and method ofminimising the risk of cross-threading during the application of athreaded cap onto a threaded neck of a container.

STATEMENT OF THE INVENTION

[0011] According to a first aspect of the present invention, there isprovided a method of applying a threaded cap to a threaded neck of acontainer, the method comprising the steps of: placing the cap on theneck of the container; rotating the cap relative to the neck in anopening direction whilst supporting the cap with respect to the neck;and applying the cap to the neck so as to achieve substantial threadengagement.

[0012] This is advantageous because if the cap is placed on the neck ofthe container with the threads of the cap and neck in misalignment, therotation of the cap in the opening direction will correct thismisalignment. This means that the threads will settle into correctalignment prior to the application of the cap onto the neck of thecontainer. This has the result that the problem of cross-threading isalleviated, thereby reducing the risk of leakage. In addition, theproblem of thread damage is also addressed.

[0013] Advantageously, the cap may be rotated relative to the neck in anopening direction through an angle of at least 360°.

[0014] Preferably, the cap is rotated relative to the neck in an openingdirection through an angle of between 36° and 720°.

[0015] Advantageously, the cap may be applied to the neck by means of anaxial force which causes the threads on the cap and the threads on theneck to move past each other and then interengage. Alternatively, thecap may be applied to the neck by rotation of the cap relative to theneck in a closing direction.

[0016] In one embodiment of the present invention the cap may bedrivingly rotated with respect to the neck by rotational drive means inboth the opening and closing directions. Alternatively the cap may bedrivingly rotated by rotational drive means in the closing direction androtated against the rotational drive means in the opening direction.

[0017] According to a second aspect of the present invention, there isprovided an applicator for applying a threaded cap to a threaded neck ofa container to achieve substantial thread engagement, the applicatorcomprising: holding means for holding at least one of the cap and thecontainer; application means for applying the cap to the neck such thatthe threads of the cap and the neck are substantially fully engaged; andmeans for rotating the cap relative to the neck in an opening directionwhilst supporting the cap with respect to the neck, such that thethreads of the neck and the cap are in alignment prior to application ofthe cap to the neck.

[0018] Advantageously, the application means may comprise means forapplying an axial force to at least one of the cap and the neck in thedirection of the other of the cap and the neck such that the threads onthe cap and the threads on the neck move past each other andinterengage. Alternatively, the application means may comprise means torotate the cap relative to the neck in a closing direction. Preferably,the application means comprises rotational drive means.

[0019] Advantageously, the means for rotating the cap relative to theneck in an opening direction may comprise a second rotational drivemeans different from said rotational drive means to drivingly rotate thecap relative to the neck in a closing direction, the applicator furthercomprising means to selectively activate one of the two rotational drivemeans.

[0020] Alternatively, the rotational drive means may be coupled to theholding means via a gear box, the rotational drive means being adaptedto selectively rotate the holding means in one of both an openingdirection and a closing direction.

[0021] In a further alternative, the rotational drive means may becoupled to the holding means by clutch means, the holding means beingadapted to be rotated against the clutch means in a direction oppositeto the direction of rotation of the rotational drive means. Preferably,engagement means are provided to engage the holding means and rotate theholding means in an opening direction against the direction of rotationof the rotational drive means.

[0022] Advantageously, the engagement means comprises a first formationwhich positively engages with a second formation provided on the holdingmeans, relative movement between the first and second formations causingthe cap to rotate with respect to the neck in an opening direction.Alternatively, the engagement means comprises a first surface whichfrictionally engages a second surface provided on the holding means,relative movement between the first and second surfaces causing the capto rotate with respect to the neck in an opening direction.

[0023] Advantageously, the duration of engagement between the engagementmeans and the holding means causes the cap to rotate with respect to theneck through an angle of at least 360°.

[0024] Preferably, the duration of engagement between the engagementmeans and the holding means causes the cap to rotate with respect to theneck through an angle of between 36° and 720°.

[0025] Advantageously, the applicator comprises a plurality of holdingmeans, each for holding at least one of a respective cap and containercombination, the rotational drive means being common to each of theplurality of holding means. Preferably, the rotational drive means iscoupled to each of the plurality of holding means via respective clutchmeans such that one or more of the holding means may be rotated againstthe respective clutch means in a direction opposite to the direction ofrotation of the rotational drive means while the remainder of theplurality of holding means are rotated in the direction of therotational drive means. Preferably, the engagement means is common tothe plurality of holding means.

[0026] According to a third aspect of the present invention, there isprovided a reverse drive mechanism for use with an applicator forapplying a threaded cap to a threaded neck of a container to achievesubstantial thread engagement, the applicator comprising holding meansfor holding at least one of the cap and the container; rotational drivemeans to rotate the cap relative to the neck in a closing direction suchthat the threads of the cap and the neck are substantially fullyengaged; and clutch means interposed between the rotational drive meansand the holding means such that the holding means is adapted to berotated against the clutch means in a direction opposite to thedirection of rotation of the rotational drive means, the reverse drivemechanism comprising engagement means to engage the holding means androtate the holding means in an opening direction against the directionof rotation of the rotational drive means whilst supporting the cap withrespect to the neck such that the threads on the neck and the cap are inalignment prior to the rotational drive means rotating the cap relativeto the neck in a closing direction.

[0027] Advantageously, the engagement means comprises a first formationwhich positively engages with a second formation provided on the holdingmeans, relative movement between the first and second formations causingthe cap to rotate with respect to the neck in an opening direction.

[0028] Alternatively, the engagement means may comprise a first surfacewhich fictionally engages a second surface provided on the holdingmeans, relative movement between the first and second surfaces causingthe cap to rotate with respect to the neck in an opening direction.

[0029] Advantageously, the duration of engagement between the engagementmeans and the holding means causes the cap to rotate with respect to theneck through an angle of at least 360°.

[0030] Preferably, the duration of engagement between the engagementmeans and the holding means causes the cap to rotate with respect to theneck through an angle of between 36° and 720°.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] An embodiment of the present invention will now be described byway of example with references to the accompanying drawings in which:

[0032]FIG. 1 shows a schematic plan view of a filling station embodyingthe present invention,

[0033]FIG. 2 shows a side view of a capping station of the fillingstation of FIG. 1,

[0034]FIG. 3 shows a side view of a capping head used in the cappingstation of FIG. 2, and

[0035]FIG. 4 shows a side elevation of a capping station embodying thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] Referring to FIG. 1, there is shown an example of a fillingstation 2 in which containers, not shown, are filled, for example, witha liquid. The containers are then closed with a cap before moving on tobe further processed if required. The neck of the container and the caphave complementary threads for resealable engagement of the container bythe cap. It will be understood that either the cap will be internallythreaded and the neck externally threaded or else the cap externallythreaded and neck internally threaded.

[0037] As can be seen in FIG. 1, the containers enter the fillingstation at the container in-feed 2 and are transported onto a firsttransfer wheel 4. In the example shown, this transfer wheel rotatesabout an axis in an anticlockwise direction. The first transfer wheel 4is located adjacent the filler 6 which is rotating about an axis in theopposite direction to the first transfer wheel 4. The filler 6 has aradius greater than that of the first transfer wheel 4.

[0038] Once the containers are transferred to the filler 6 they aretransported around the circumference of the filler and are filled withthe desired material, for example a potable liquid. Once the containershave been filled they continue around the circumference of filler 6until they reach a second transfer wheel 8.

[0039] The second transfer wheel 8 rotates about an axis in a directionopposite to that of the filler 6, shown as anti-clockwise. When thecontainers are transferred to the second transfer wheel 8 they movearound the circumference of the second transfer wheel 8 and pass beneatha cap placement point 10. The cap placement point 10 is not shown indetail, but it is here that a cap is placed or otherwise rested on theneck of the container such that the threads of the cap and neck of thecontainer are not significantly engaged. This placement may be by meansof either the “pick and place” method or “pick-off” method previouslydescribed. At a point on the circumference of the second transfer wheel8, after the containers have passed under the cap placement point 10,the containers are transferred to a capping station 12. Capping station12 rotates about an axis in a direction opposite to that of the secondtransfer wheel 8, shown as clockwise.

[0040] The capping station 12 has a number of capping heads 14 whichrotate about the axis of the capping station 12. When the container isbeing transported around the axis of the capping station 12, it isbrought into contact with a capping head 14 and the cap is applied tothe neck of the container such that the threads of the cap and thethreads of the container become substantially fully engaged.

[0041] At a point on the circumference of the capping station 12, andafter the cap has been applied to the container neck, the container ispassed to a third transfer wheel 16. The third transfer wheel 16 rotatesabout an axis in a direction opposite to that of the capping station,shown as anticlockwise. The containers, which are now filled and sealed,are removed from the filling station 1 by the third transfer wheel 16along out-feed 18 prior to any necessary further processing.

[0042]FIG. 2 shows a side view of a capping station 12 such as that usedin the filling station of FIG. 1. A container 20 has a neck 22 on whichhas been placed a cap 24. The container 20 is supported on a stand 26.The stand 26 is capable of translational motion by virtue of a rollingsupport member 28, the stand being located on a platform 30. Thecontainer 20 is held within two pairs of retaining rails 32 (only one ofwhich is shown) located on opposite sides of the container 20. Locateddirectly above container 20 is a capping head 14, which will bediscussed in greater detail below. The capping head 14 is attached viashaft 34 to capping station 12.

[0043] The arrow on FIG. 2 shows the direction of motion of thecontainer 20 as it moves in the capping station 12. The stand 26 andcontainer 20 move at substantially the same speed as the capping head14, so that the container 20 and capping head 14 remain in direct axialalignment. As the container moves along the platform 30 it is elevatedat step 36, so that the cap 24 is received within the capping head 14.At this point it is possible for the final application of the cap 24 tothe neck 22 to take place, so that the threads of the cap and the neckcome into substantially full engagement.

[0044]FIG. 3 shows a detailed side view of a capping head 14, such asthat used in FIG. 2. The capping head comprises a chuck 38, in which isprovided a cap recess 40. The cap recess 40 is sized such that a cap 24received within the cap recess can be gripped sufficiently so that anytorque applied to the capping head 14 will be directly applied to thecap 24. This transfer of torque from the capping head 14 to the cap 24may be achieved by means of a frictional material within the cap recess40, or by any other method, for example the positive engagement of aformation provided on the capping head with a corresponding formationprovided on the cap.

[0045] The chuck 38 is coupled to shaft 34 via a head load spring 42.The head load spring 42 provides a resilience to the capping head 14 onthe axial direction. Above the head load spring 42, the shaft 34 isattached to a clutch mechanism 44, which may take any of the followingforms, electrical, magnetic or mechanical. The capping head 14 is thenattached to a motor, not shown, which provides rotational drive to thecapping head 14, to rotate the cap 24 with respect to the container 20until a predefined torque is achieved between the cap 24 and the neck22.

[0046] As has been previously discussed, a problem has been identifiedin that the threads of the cap and neck can become cross-threaded duringthe initial placement of the cap on to the neck. A method of solvingthis problem is to initially rotate the cap in an opening direction,such that any misalignment is corrected, prior to subsequently applyingthe cap to the container neck.

[0047] In one embodiment of the present invention there is provided acapping head 14 which is coupled to both a first and a second motor.These motors provide rotational drive in both a clockwise andanticlockwise direction. One of these directions will rotate the cap 24relative to the neck 22 in an opening direction and the other willrotate the cap 24 relative to the neck 22 in a closing direction. Meansare provided on the capping station 12 to selectively couple the cappinghead 14 first to that motor which rotates the cap in the openingdirection and then to that motor which rotates the cap in the closingdirection. The ability of the capping station 12 to provide both anopening and closing rotation to the cap 24 will prevent anycross-threaded caps from being applied to the container neck and soremove one cause of subsequent leakage.

[0048] The capping head 14 in this particular embodiment rotates in anopening direction after the cap has been placed on the neck 22 of thecontainer and after the cap has been received in the cap recess 40 ofthe capping head 14. This opening rotation should be through an anglesufficient to uncross the threads. For example in a cap having fourstarts the rotation is preferably through an angle of at least 90°.However, it will be understood that the opening rotation may be throughany number of turns sufficient to remove cross-threading and may, forexample, be through an angle within the range from 36° and 720°.Subsequent to the rotation in the opening direction the secondrotational drive rotates the capping head 14, and therefore the cap 24,in a closing direction, until a predetermined torque is achieved betweenthe cap and the neck of the container.

[0049] In a second embodiment of the present invention the capping head14 is coupled to only one motor but that motor is in turn coupled to agear box and the capping head is coupled to the output of the gear box.The gear box enables the rotational drive from the motor to be providedto the capping head 14 in either an opening or a closing direction.Again, means are provided to selectively actuate the gear box so thatthe capping head is initially rotated in an opening direction beforesubsequently being rotated in a closing direction. This results in amethod of addressing the risk of cross-threading similar to thatdescribed with respect to the first embodiment, but without the need fora second rotational drive motor.

[0050] In a further embodiment of the invention a single motor isprovided to rotate the capping head 14 in a direction that will rotatethe cap in a closing direction with respect to the container neck.However, the motor is coupled to the capping head 14 by means of aclutch. The provision of a clutch enables the capping head to beforceably rotated in a direction opposite to the direction of rotationof the motor without damaging the motor or any of its constituent parts.

[0051]FIG. 4 shows part of a capping station in accordance with thisfurther embodiment. The capping station 12 comprises eight capping heads14 rotating in a circle indicated by arrows 46 about an axis of thecapping station. In addition, each capping head 14 is rotating about itsown axis, indicated by arrows 48, under the action of a common motor(not shown). However, each capping head 14 is coupled to that commonmotor by means of a respective clutch, also not shown. Each of thecapping heads 14 is provided with a shoulder 50 which may be formed onthe chuck 38 or else as an annular protrusion on the shaft 34. A plate52 is provided to one side of the capping station 12 and as the cappingheads 14 rotate about the axis of the capping station as indicated byarrows 46 so each of the shoulders in turn engage a surface of plate 52.As the capping heads 14 continue to rotate about the axis of the cappingstation 12 so the shoulder 50 slides along the plate 52. At the sametime, the frictional engagement between the shoulder 50 and the plate 52causes the capping head in engagement with the plate to rotate againstits clutch in a direction opposite to that in which it is being drivenby the motor. This in turn results in the cap received within the chuck38 being rotated in an opening direction with respect to the containerneck. However, as soon as the capping head 14 moves out of engagementwith the plate 52, the frictional engagement responsible for the reverserotation is removed thereby enabling the motor to resume rotation of thechuck 38 in a direction that will be rotate the cap in a closingdirection with respect to the container neck. This particularly elegantmeans of providing a reverse drive can be retrofitted to existingcapping machines to alleviate the problems associated withcross-threading between caps and container necks. The plate 52 ispreferably of a length to ensure a reverse rotation of at least 360°although it will be understood that, depending on the number of startsand the length of the threads involved, a reverse rotation of between36° and 720° may be sufficient to alleviate the problem. Preferably theplate 52 is biaised in the direction of arrows 54 to ensure thenecessary frictional engagement with shoulder 50.

[0052] Although in this last embodiment the reverse rotation of thecapping head 14 has been described as by means of the frictionalengagement of the plate 52 with the shoulders 50, it will be understoodthat means may be provided to positively engage each of the cappingheads in turn and so rotate the capping head against the clutch in adirection opposite to the direction of rotation of the motor. Forexample, the plate 52 may be replaced by a rack having teeth which mightengage with corresponding teeth provided on the capping heads 14.

1. A method of applying a threaded cap to a threaded neck of acontainer, the method comprising the steps of: placing the cap on theneck of the container; rotating the cap relative to the neck in anopening direction whilst supporting the cap with respect to the neck;and applying the cap to the neck so as to achieve substantial threadengagement.
 2. A method as claimed in claim 1, wherein the cap isrotated relative to the neck in an opening direction through an angle ofat least 360°.
 3. A method as claimed in claim 1, wherein the cap isrotated relative to the neck in an opening direction through an angle ofbetween 36° and 720°.
 4. A method as claimed in claim 1, wherein the capis applied to the neck by means of an axial force which causes thethreads on the cap and the threads on the neck to move past each otherand then interengage.
 5. A method as claimed in claim 1, wherein the capis applied to the neck by rotation of the cap relative to the neck in aclosing direction.
 6. A method as claimed in claim 5, wherein the cap isdrivingly rotated with respect to the neck by rotational drive means inboth the opening and closing directions.
 7. A method as claimed in claim5, wherein the cap is drivingly rotated by rotational drive means in theclosing direction and is rotated against the rotational drive means inthe opening direction.
 8. An applicator for applying a threaded cap to athreaded neck of a container to achieve substantial thread engagement,the applicator comprising: holding means for holding at least one of thecap and the container; application means for applying the cap to theneck such that the threads of the cap and the neck are substantiallyfully engaged; and means for rotating the cap relative to the neck in anopening direction whilst supporting the cap with respect to the neck,such that the threads of the neck and the cap are in alignment prior toapplication of the cap to the neck.
 9. An applicator as claimed in claim8, wherein the application means comprises means for applying an axialforce to at least one of the cap and the neck in the direction of theother of the cap and the neck such that the threads on the cap and thethreads on the neck move past each other and interengage.
 10. Anapplicator as claimed in claim 8, wherein said application meanscomprises means to rotate the cap relative to the neck in a closingdirection.
 11. An applicator as claimed in claim 10, wherein saidapplication means comprises rotational drive means.
 12. An applicator asclaimed in claim 11, wherein said means for rotating the cap relative tothe neck in an opening direction comprises a second rotational drivemeans different from said rotational drive means to drivingly rotate thecap relative to the neck in a closing direction, the applicator furthercomprising means to selectively activate one of said two rotationaldrive means.
 13. An applicator as claimed in claim 11, wherein saidrotational drive means is coupled to said holding means via a gear box,said rotational drive means being adapted to selectively rotate saidholding means in one of both an opening direction and a closingdirection.
 14. An applicator as claimed in claim 11, wherein saidrotational drive means is coupled to said holding means via clutchmeans, said holding means being adapted to be rotated against saidclutch means in a direction opposite to the direction of rotation ofsaid rotational drive means.
 15. An applicator as claimed in claim 14,wherein engagement means are provided to engage said holding means androtate said holding means in an opening direction against the directionof rotation of said rotational drive means.
 16. An applicator as claimedin claim 15, wherein said engagement means comprises a first formationwhich positively engages with a second formation provided on saidholding means, relative movement between said first and secondformations causing said cap to rotate with respect to the neck in anopening direction.
 17. An applicator as claimed in claim 15, whereinsaid engagement means comprises a first surface which frictionallyengages a second surface provided on said holding means, relativemovement between said first and second surfaces causing said cap torotate with respect to the neck in an opening direction.
 18. Anapplicator as claimed in claim 15, wherein the duration of engagementbetween said engagement means and said holding means causes said cap torotate with respect to the neck through an angle of at least 360°. 19.An applicator as claimed in claim 15, wherein the duration of engagementbetween said engagement means and said holding means causes said cap torotate with respect to the neck through an angle of between 36° and720°.
 20. An applicator as claimed in claim 11 comprising a plurality ofholding means, each for holding at least one of a respective cap andcontainer combination, said rotational drive means being common to eachof said plurality of holding means.
 21. An applicator as claimed inclaim 20, wherein said rotational drive means is coupled to each of saidplurality of holding means via respective clutch means such that one ormore of said holding means may be rotated against said respective clutchmeans in a direction opposite to the direction of rotation of saidrotational drive means while the remainder of the plurality of holdingmeans are rotated in the direction of said rotational drive means. 22.An applicator as claimed in claim 21, wherein said engagement means iscommon to said plurality of holding means.
 23. A reverse drive mechanismfor use with an applicator for applying a threaded cap to a threadedneck of a container to achieve substantial thread engagement, theapplicator comprising: holding means for holding at least one of the capand the container; rotational drive means to rotate the cap relative tothe neck in a closing direction such that the threads of the cap and theneck are substantially fully engaged; and clutch means interposedbetween said rotational drive means and said holding means such that theholding means is adapted to be rotated against said clutch means in adirection opposite to the direction of rotation of said rotational drivemeans, the reverse drive mechanism comprising engagement means to engagesaid holding means and rotate said holding means in an opening directionagainst the direction of rotation of said rotational drive means whilstsupporting the cap with respect to the neck such that the threads on theneck and the cap are in alignment prior to said rotational drive meansrotating the cap relative to the neck in a closing direction.
 24. Areverse drive mechanism as claimed in claim 23, wherein said engagementmeans comprises a first formation which positively engages with a secondformation provided on said holding means, relative movement between saidfirst and second formations causing said cap to rotate with respect tothe neck in an opening direction.
 25. A reverse drive mechanism asclaimed in claim 23, wherein said engagement means comprises a firstsurface which frictionally engages a second surface provided on saidholding means, relative movement between said first and second surfacescausing said cap to rotate with respect to the neck in an openingdirection.
 26. A reverse drive mechanism as claimed in claim 23, whereinthe duration of engagement between said engagement means and saidholding means causes said cap to rotate with respect to the neck throughan angle of at least 360°.
 27. A reverse drive mechanism as claimed inclaim 23, wherein the duration of engagement between said engagementmeans and said holding means causes said cap to rotate with respect tothe neck through an angle of between 36° and 720°.